Harold Taylor

Bio: Harold Taylor is an academic researcher from Research Triangle Park. The author has contributed to research in topics: Antimutagenic Agents & Quassinoid. The author has an hindex of 15, co-authored 25 publications receiving 4163 citations.

Plant antimutagenic agents, 2. Flavonoids.

Abstract: A number of known prenylated flavonoids were isolated from Psoralea corylifolia using an assay procedure based on inhibition of the mutagenic action of 2-aminoanthracene on Salmonella typhimurium (T-98). All of these compounds were toxic rather than antimutagenic or desmutagenic. Bakuchiol [17], a known prenylated phenolic terpene, was also isolated; its activity was not due to toxicity. Biochanin A [4], a known isoflavone, was similarly isolated from Cicer arientinum and was active and nontoxic. Some of the above flavonoids were studied for inhibition of the mutagenicity of several different mutagens with results depending upon the structure of the flavonoid and the mutagen.

Plant antitumour agents: colubrinol acetate and colubrinol, antileukaemic ansa macrolides from Colubrina texensis

Abstract: The isolation and structures of two new antileukaemic ansa macrolides, colubrinol acetate (1) and colubrinol (2), have been described.

Plant antimutagens, 6. Intricatin and intricatinol, new antimutagenic homoisoflavonoids from Hoffmanosseggia intricata.

Abstract: Intricatin [1] and intricatinol [2] are new homoisoflavonoids isolated from a desert plant Hoffmanosseggia intricata, which was collected in Baja California, Mexico. The structures of the compounds were elucidated using a variety of spectroscopic techniques. The structure of 1 was shown to be 7,4'-dimethoxy-8-hydroxyhomoisoflavone, and 2 was shown to be 4'-methoxy-7,8-dihydroxyhomoisoflavone. Both compounds 1 and 2 displayed activity in the inhibition of the mutagenicity of 2AN toward Salmonella typhimurium (T98). Compound 2 was much more active than 1 in the case of the inhibition of the mutagenicity of AAF toward S. typhimurium (T98) and the inhibition of EMS towards S. typhimurium (T100). Compounds 1 and 2 are the first examples of antimutagenic activity in homoisoflavones.

Plant Antimutagenic Agents, 1. General Bioassay and Isolation Procedures

Abstract: An antimutagenic assay in Salmonella typhimurium has been utilized for a study of the inhibition of the mutagenic activity of 2-aminoanthracene in the presence of the Ames S-9 metabolic activation preparation by crude organic solvent extracts of plant materials. More than 2000 extracts representing 39 families have been tested to date. Confirmed inhibitory activity has been found in 80 samples. More than 60% were nontoxic. Methods for isolation and characterization of pure compounds are presented. Of particular interest is the utilization of large scale preparative hplc for rapid purification of inhibitory chromatographic fractions that were still highly impure.

Microtubules as a target for anticancer drugs.

Abstract: Highly dynamic mitotic-spindle microtubules are among the most successful targets for anticancer therapy. Microtubule-targeted drugs, including paclitaxel and Vinca alkaloids, were previously considered to work primarily by increasing or decreasing the cellular microtubule mass. Although these effects might have a role in their chemotherapeutic actions, we now know that at lower concentrations, microtubule-targeted drugs can suppress microtubule dynamics without changing microtubule mass; this action leads to mitotic block and apoptosis. In addition to the expanding array of chemically diverse antimitotic agents, some microtubule-targeted drugs can act as vascular-targeting agents, rapidly depolymerizing microtubules of newly formed vasculature to shut down the blood supply to tumours.

Promotion of microtubule assembly in vitro by taxol

Abstract: TAXOL (Fig. 1) was isolated from the plant Taxus brevifolia (western yew) by Wani et al., who reported that the molecule has antitumour activity in several experimental systems1. In our laboratory we have found that taxol, a low molecular weight neutral compound, completely inhibits division of exponentially growing HeLa cells at low concentrations of drug (0.25 µM) that have no significant effects on DNA, RNA or protein synthesis during a 4-h incubation with the cells. HeLa cells incubated with taxol for 20 h are blocked in late G2 and/or M (ref. 2). We report here that taxol acts as a promoter of calf brain microtubule assembly in vitro, in contrast to plant products such as colchicine and podophyllotoxin, which inhibit assembly. Taxol decreases the lag time for microtubule assembly and shifts the equilibrium for assembly in favour of the microtubule, thereby decreasing the critical concentration of tubulin required for assembly. Microtubules polymerised in the presence of taxol are resistant to depolymerisation by cold (4 °C) and CaCl2 (4 mM).

Bioprospecting for Microbial Endophytes and Their Natural Products

Abstract: Endophytic microorganisms are to be found in virtually every plant on earth. These organisms reside in the living tissues of the host plant and do so in a variety of relationships, ranging from symbiotic to slightly pathogenic. Because of what appears to be their contribution to the host plant, the endophytes may produce a plethora of substances of potential use to modern medicine, agriculture, and industry. Novel antibiotics, antimycotics, immunosuppressants, and anticancer compounds are only a few examples of what has been found after the isolation, culture, purification, and characterization of some choice endophytes in the recent past. The potential prospects of finding new drugs that may be effective candidates for treating newly developing diseases in humans, plants, and animals are great.

Taxol stabilizes microtubules in mouse fibroblast cells.

Abstract: Taxol, a potent inhibitor of human HeLa and mouse fibroblast cell replication, blocked cells in the G2 and M phase of the cell cycle and stabilized cytoplasmic microtubules. The cytoplasmic microtubules of taxol-treated cells were visualized by transmission electron microscopy and indirect immunofluorescence microscopy. More than 90% of the cells treated with 10 micro M taxol for 22 hr at 37 degrees C displayed bundles of microtubules that appeared to radiate from a common site (or sites), in addition to their cytoplasmic microtubules. Untreated cells that were kept in the cold (4 degrees C) for 16 hr lost their microtubules, whereas cells that were pretreated with taxol for 22 hr at 37 degrees C continued to display their microtubules and bundles of microtubules in the cold. Taxol inhibited the migration behavior of fibroblast cells, but these cells did not lose their ability to produce mobile surface projections such as lamellipodia and filopodia.